Synthesis of biotin intermediates



Patented Apr. 5, 1949 UNI TE D STAT ES P AT EN OFFICE I 2466,2325; I a A SYNTHESIS OF BIOTIN Stanton A'QHari'is; wstfiela ananominee-Hem,

\ No Drawing. Aii'fil'ication sp teiiiiir 16, 1944,

Serial No. 55 1,"15 8 4 Claims, (01. 2664176 This invention is concerned generally with novel chemical compounds and processes ofpreparing the same; more particularly-it relates to novel compounds useful as intermediates in synthesis of the growth-promotingfactor, biotin;

Biotin is known to be one of the'isomers of the chemical compound 2- (4'-carboxy-butyl) -314- ureido-tetrahydrothiophene, having the empirical formula CH1603N2S, and the structural formula:

0 HN-(LNH H H mo-s-onomonzomomooan It is now found that this compound can be synthesized by reactions indicated as follows; 7

--- m-Memorials on 4 [LOB-ta t. g

solution tovyield 2eacylamido s-carboxymethylmercapto-propanoic acid (3). This product is esterifled using a mineral :acid. catalyst; to pro duce the diester (4) ofwthe acid (3) ,uand the diester is treated with alkali metal alcoholate or an alkalineearth metal alcoholate to yield the. 2-alkali metal or the .2.-alkaline earth ,metal derivative tofu, an ester of 210ml QXYr-Ii-keto 4-v acylamido:tetrahydrothiophene.(5).., 'Ihisv com--- pound,- -,whenr, heated, with a dilute mineral acid,

is hydrolyzedl'and decarboxylated' 219C111??? produces an equilibrium mixture of 2-(4-car"-- boxy-butylidene) -3 4-di(acylamido) -tetrahydrothiophene ester (9a) and 2-(4carboxy-butyD- 3 :4 di(acylamido) 4: 5 dihydrothiophene ester (9b). This equilibrium mixture, or ifv preferred, one of the equilibrants, is then treated with hydrogen in the presence of a hydrogenation catalyst to yield 2-(4'-carboxy-butyl)'-3z4 di(acylamido)-tetrahydrothiophene ester (10). When this last mentioned compound is treated with an aqueous alkaline solution, hydrolysis of the acyl groups occurs, yielding upon acidification, 2 (4' carboxy-butyl) -3:4-diamino-tetrahydrothiophene (11) which, when reacted with a carbonyl halide, produces the compound 2-(4- carboxy-butyl) -3 :4 ureido-tetrahydrothiophene. This product is obtained as a mixture of stereoisomers, one of which is racemic biotin, from which upon resolution, is obtained the dextrorotatory isomer, biotin.

Intermediate 4 above can be prepared as indicated above in general terms and as described in detail in concurrently filed application, Serial No- 554,449; it is converted to biotin through the operations indicated above in general terms and as described in detail in concurrently filed applications, Serial Nos. 554,450, 554,451, 554,452, now Patent No. 2,452,653; 554,453, now Patent No. 2,460,224; 554,454, now Patent No. 2,459,817; 554,455, 554,456, 554,457, 554,459, new Patent No. 2,437,719; 554,460, now Patent No. 2,442,681; and 554,461, now Patent No. 2,441,141.

The present invention is concerned with an alternative process for the synthesis of the intermediate above mentioned, a diester of 2-acylamido-3-carboxymethylmercapto propanoic acid. According to this alternative process this compound is obtained by reactions indicated enerally as follows:

RNH thionyl RNH (I: 01 MSCHzC 03B."

H-C 0 R phosphorous C H.C 0 R H 011 halide HgX E1131 (4) C H-C-OaR' these radicals can be varied without effect upon the process. For example, R can be acetyl, propionyl or benzoyl; R and/or R" can be methyl, ethyl, propyl, butyl, benzyl or the like. Thionyl or phosphorous chlorides and bromides being most readily available, it is preferred that X be C1 or Br, andfor similar reasons, that M be Na or K.

The following example illustrates a method of carrying out the present invention, but it is to be understood that this example is given by way of illustration and not of limitation.

Example About 1.3 g. of the ethyl ester of Z-benzamido- 3-hydroxy-propanoic acid (which can be prepared. by reacting 2-amino-3-hydroxy-propanoic acid with benzoyl chloride in presence of an alkali, followed by esterification) is suspended in benzene, about 0.4 cc. of pyridine is added followed byapproximately 0.6 cc. of thionyl chloride, and the mixture is heated on a steam bath for about 20 minutes, then cooled. It is washed with water,

dilute hydrochloric acid, dilute sodium bicarbonate solution, again with water; the benzene is removed in vacuo and the residue is crystallized from other and petroleum ether, yielding the product: ethyl ester of 2-benzamido-3-chloropropanoic acid (M. P. 90.5-9l 0.). About 1.8 g.

of this ester dissolved in a little alcohol is added toa solution formed by dissolving about .16 g. of sodium in absolute ethanol and adding 0.85 g. of ethyl thioglycolate, and the mixture is heated on a steam bath for about 20- minutesv or until neutral (using litmus indicator), then it is filtered, the alcohol is removed invacuo, the residue is taken up in ether, filtered, the ether is distilled and an oily residue is obtained comprising the diethyl ester of 2-benzamido3-carboxymethylmercapto-propanoic acid. When treated with sodium ethoxide ring closure is efiected and, upon decarboxylation by heating with an aqueous acid, 3-keto-4-benzamido-tetrahydrotl'riophene (intermediate 6 above) is obtained.

In like manner by using as starting materials the methyl or propyl esters of 2-benzamido-3-hydroxy-propanoic acid with ethyl thioglycolate corresponding mixed diesters can be obtained or if preferred corresponding esters of thioglycolic acid can be used to produce corresponding diesters having the same alkyl groups.

Modifications may be made in carrying out the present invention, without departing from the spirit and scope thereof and the invention is to be limited only by the appended claims.

What is claimed is:

l. The process that comprises reacting under alkaline conditions a lower alkyl ester of thioglycolic acid with a lower alkyl ester of 2-benzamido- 3-chloro-propanoic acid to form an ester of 2- benzamido-3-carboxymethylmercaptopropanoic acid.

2. The process that comprises reacting under alkaline conditions, the ethyl ester of 2-benzamido-3-chloro-propanoic acid with ethyl thioglycolate to produce the diethyl ester of 2-benzamido- 3 -carboxymethyl mercapto propanoic acid.

3. The process that comprises reacting ethyl- 2-benzamido-3-chloro-propanoate with an S- alkali metal derivative of ethyl thioglycolate to produce diethyl-2-benzamido-3-carboxymethylmercapto-propanoate.

4. The process that comprises reacting ethyl-2- benzamido-3-chloro-propanoate with the S-sodium derivative of ethyl thioglycolate to produce diethyl-2 -b enzamido-S-carboxymethylmercapto propanoate.

STANTON A. HARRIS. DOROTHEA HEYL.

(References on following page) Michaelis et al., "J. Biol. Chem, vol. 106, pp. REFERENCES CITED 331441 G934 The following references are of record in the K rr 1; a1 Helv, hi ta, ol, 27, ar, file of this patent: 15, 1944, pp. 237-239.

Bergmann et a1" ph i l chemun VOL 5 Karrer et aL, Helv. Ch1m. Acta, vol. 27, July 140, pp. 128445 (1924). 1944 12814282- Karrer et a1., Helvetica Chim. Acta, v01. 9, 301-323 (1926). 

